Quantitation of myocardial infarction (MI) weight, the degree of cardiac ischemia, and the amount of left ventricular (LV) dysfunction associated with acute myocardial infarction (AMI) should be valuable in understanding the natural history of AMI and the post-MI course in man. Similar quantitative knowledge of the extent and degree of cardiac ischemia would be useful in judging objectively the results of coronary artery bypass (CAB) surgery. We will employ radionuclear methods (myocardial infarction scintiphotos (S), radionuclear angiocardiography) and the continuously recorded modified Frank Vectorcardiogram (to define the ST-segment vector magnitude) to characterize infarct size, LV contractility and wall motion, and relative myocardial ischemia, respectively, during AMI. Also we will assess the degree of LV dysfunction and ischemia at 6 months post-MI. These studies may allow greater objective definition of the above variables and may allow characterization of high and low risk subsets for the development of complications during AMI and post-MI. Such subsets may include risk of reinfarction, sudden death, and congestive cardiac failure. We will perform S and radionuclear angiocardiography at rest and exercise before and after CAB. Such noninvasive studies may provide objective data about the strengths and limitations of these methods, functional results of CAB, and about the effects of perioperative MI on LV contractility.